Hakyeon Kim. 1999. An Optimality Analysis of Null Arguments. Studies in Modern Grammar 16, 121-138. The aim of this paper is to survey the distribution of null subjects and null objects found in Korean and to show that the previous approaches to explain their licensing have not been so successful. We will also show that the licensing of the null arguments are better explained through the methodology of Optimality theory. In accordance with the optimality theory, the constraint ranking such as DropTopic = Parse or DropTopic ＞＞ Parse can solve the problems remained in control theory and Huang`s generalized control rule because by changing the constraint ranking even the pro-drop parameters can be explained better. Particularly the asymmetry found in the licensing of null subjects and null objects can be solved with a couple of constraints. However, there remain some detailed problems in the licensing related with pragmatic context and some idiosyncratic features of individual word. And further research for the interpretation of null arguments in Optimality methodology is expected.